Broadhead arrowheads are typically those utilized for hunting midsize to large game animals. These arrowheads provide large cutting diameters to provide large wound channels leading to rapid exsanguination, providing an ethical kill.
In the archery industry, broadheads are made in two different configurations: fixed blade or expandable/“mechanical” broadhead. A fixed blade broadhead has blades immovably attached to a central ferrule. Fixed blades add surface area to an arrow's aerodynamic profile, reducing the accuracy of an arrow shot with a fixed blade broadhead attached.
With mechanical broadheads, the blades are closed, folded, or at least partially stowed in the ferrule before deployment. When the blades are not deployed, the surface area or profile of the arrowhead is reduced, increasing accuracy. On impact with a target, the blades deploy to provide a larger cutting diameter than could be provided by equally accurate arrowheads having fixed blades.
A variety of mechanisms are used to maintain a stowed or deployed position of the blades. A technique for retaining blades includes providing O-rings about the blades which are cut or roll to the base of the arrowhead or shaft of the arrow on impact, allowing the blades to deploy. Other techniques utilize various mechanisms based on the interaction of solid, inflexible components which may become seized if not maintained or if contaminants are encountered. Because mechanical broadheads include moving parts, problems can arise in their use. Failure to deploy, early deployment, or loss of energy needed for effective penetration all decrease the likelihood of recovering hit game.
When blades fail to deploy, the wound channel may be insufficient to inflict the damage required for fast expiry. When blades deploy early, or when penetrating energy is lost, the wound channel may not be deep enough to reach the target's vital organs, or the arrow may lose its trajectory or deflect. Effective penetration is especially critical to ethical harvest when the arrow strikes a bone such as a rib or scapula. Further, after an ideal hit with sufficient penetration, the arrow will exit through the animal, increasing the likelihood of an easily-tracked blood trail and speedy recovery of the harvested animal.
However, it is nearly inevitable that a broadhead will encounter bone or other harder tissue (e.g, cartilage) in addition to passing through skin, fat, muscle, and organs. To facilitate deep penetration and the production of exit wounds, it would be beneficial for a broadhead to maximize cutting diameter through soft tissue while flexing around hard tissue to avoid loss of penetration or significant deflection from the targeted vital portions of the body.